Peculiarities of the Variation of Biologically Active Compounds in Fruit of Vaccinium oxycoccos L. Growing in the Čepkeliai State Strict Nature Reserve

This study was carried out to analyze the accumulation patterns of anthocyanins, proanthocyanidins, flavonols, chlorogenic acid, and triterpene compounds in fruit samples of Vaccinium oxycoccos L. berries growing in the Čepkeliai State Strict Nature Reserve in Lithuania. Studies were carried out on the phytochemical composition of cranberry fruit samples during the period of 2020–2022. Anthocyanins, flavonols, chlorogenic acid and triterpene compounds were identified and quantified using UPLC-DAD methods, and proanthocyanins were determined using spectrophotometric methods. The content of identified compounds varied, as reflected in the total amounts of anthocyanins (710.3 ± 40 µg/g to 6993.8 ± 119 µg/g), proanthocyanidins (378.4 ± 10 µg EE/g to 3557. 3 ± 75 µg EE/g), flavonols (479.6 ± 9 µg/g to 7291.2 ± 226 µg/g), chlorogenic acid (68.0 ± 1 µg/g to 3858.2 ± 119 µg/g), and triterpenoids (3780.8 ± 98 µg/g to 7226.9 ± 224 µg/g). Cranberry fruit samples harvested from open oligotrophic wetland habitats contained higher levels of anthocyanins, anthocyanidins, flavonol glycosides, and proanthocyanidins. The highest levels of triterpene compounds were found in the cranberry fruits harvested in the spring of the following year after the snowmelt. The use of principal component analysis showed that cranberry plant material harvested in October and November had higher levels of bioactive compounds.